by Steve T. Davis
From the very beginnings of radio, plastic has been incorporated into the manufacture of radio cabinets and the internal workings of radios. From knobs to tube bases to platforms for components, plastic was used, not to enhance the looks of a home-brew, but as an electrical insulator. The first totally plastic radio cabinets hit the showroom floors sometime in early 1933. They didn't explode onto the scene as some might expect; instead they were offered as exotic alternatives to the millions of wooden radios already in production. With names like Air King, Colonial and Kadette, these maverick manufacturers took advantage of the latest technologies of the time. Plastic cabinets started out small compared to their wooden cousins but they were big compared to almost all other plastic items being manufactured at the time. In 1932 advertisements, Emerson offered "the world's smallest radio" which was about the size of a smallish cathedral. The very next year when Air King introduced its model 52 (the skyscraper), again about the size of a smallish cathedral, it was the largest molded piece of plastic ever attempted up to that time.
These early attempts were successful enough for manufacturers to continue offering plastic cabinets in subsequent years. Then in 1936, Sears, using its radio trade name Silvertone, introduced a plastic radio to its catalog audience. The radio had a such a classic design and low price that it became an instant mail order hit and spawned similar designs that lasted into the late 1940s.
In the last few years, pre-war plastic radios have become very desirable additions to radio collections. Frequently, when the topic of radio conversation turns to plastic, it becomes lively in discussing the differences between the types of materials, manufacturers and a confusing array of names used when describing a plastic radio. Hopefully, the information discussed below will help to dispel some rumors, provide some insight and possibly relieve some of the confusion surrounding the plastics of pre-war radios.
The first plastic radios were made of a material called bakelite. Bakelite is simply the trade name for a material invented by Leo Baekland. Mr. Baekland was a chemist from Belgium who immigrated to the U.S. around 1900. He soon began to experiment with two coal byproducts: phenol and formaldehyde. He found that when these two chemicals were mixed together under moderate heat the result was a sticky, viscous resin. When this material was then allowed to cool it would harden and in this way could be molded into shapes. Unfortunately, the new product was brittle and would break and crumble with minimal pressure. His next step was to crush the new material into a light brown fluffy powder and then resubmit it to heat and pressure but this time a lot more of both. This step permanently "set" or bonded the molecules of the two chemicals into a stable and hard material. This process became known as thermosetting. The result was a powder that could easily be put into molds to create products. In 1909, Mr. Baekland patented this new material and formed a company called Bakelite. The Bakelite Company began selling their material to many manufacturers, and became a huge success. The company kept experimenting with the material and quickly found that they could use "fillers" to make their product stronger, more durable and cheaper. The filler material was usually rags, cotton, wood flour or carbon. Even when these fillers were incorporated into the original material, the intense heat and pressure used would keep the end product a dark brown. The variations of color (mainly browns), mottling and even swirling we see today in bakelite radios are from the different fillers used. Because of the Bakelite Company's huge success, the name bakelite quickly became synonymous with thermosetting plastics in general, and is used today to describe many other early types of plastics.
Soon after Mr. Baekland's announcement of his successful work with formaldehyde and phenol, other chemists began working with different chemical mixtures looking for other compounds with thermosetting plastic characteristics. In 1921, Austrian chemists discovered that when the chemical urea was mixed with formaldehyde it too created a gooey "plastic" compound. A major difference was that when wood flour was used as a filler and the compound "set," the end product was white in color. Another difference was that the heat and pressure need to set the material was only a small portion of that needed to create bakelite. The white base color and lower setting temperatures allowed the use of certain dyes to be added to create an end product with a variety of colors.
Ironically, one of the favorable attributes of urea -- lower temperature setting -- manifests itself today in an unfavorable way. The cracks commonly referred to as "stress lines" which seemingly begin and end anywhere on the radio are caused by time completing the setting process over the years.
Plaskon was developed and introduced in 1931 by the Toledo Scale Company to incorporate into their scales to make the machines lighter and easier to ship. They began with the urea compound and used cellulose as a filler. They also made a few other chemical additions to keep the material from fading (they wanted a bright white color for the scale basin). Because of the superior properties and the help of a great marketing department, plaskon soon became the plastic of choice when a manufacturer wanted an end product to be a color other than the standard bakelite brown and black. Nearly all of the pre-war plastic radios found today that do not fit into the bakelite or catalin genre are made from plaskon.
When the last of Leo Baekland's patents expired in 1926, several chemists began experimenting with the phenol-formaldehyde compound and by 1928 had the resin refined to a clear mixture. But the problems still lingered with the heat and pressure requirements, and the fillers. The clear material couldn't stand up to the rigors of pressure molding and the fillers needed to make the material less brittle would always show through. Chemists around the world experimented for several years trying to find dyes that would hold color under the conditions needed to "set" the material. Finally, a group of chemists from a German company devised a way to make dyes directly from coal tar. Combined with varying amounts of water the dyes could be added to the resin to create a range from clear to opaque and with a variety of colors. The new dye-laden resin still couldn't stand the molding process, so instead they used a method called "casting." Casting differed from molding in several ways; the most important being that when the casting process was completed, the product still required much more work to rend the piece into its final shape. Milling, sanding, buffing and tumbling were the usual steps to a finished product.
In 1928, the American Catalin Corporation purchased the rights import the German companies dyes to the United States. Soon after, Catalin was licensed to several firms such as Marblette, Joanite, Fiberloid, Du Pont and even Bakelite. These companies sold resin mostly to be used in costume jewelry, novelty items, decorative, handles, napkin rings, and other small products. The fact that considerable milling was involved kept the products simple and usually small. The popularity of bakelite and plaskon with radio consumers and their demand for color variety brought Catalin to the manufacturers' attention. In 1937 Emerson, Fada and other radio manufacturers started to use Catalin and its licensed suppliers to produce cabinets. The milling required on such complex pieces was intense and damage by handling occurred often. Another factor of concern to catalin radio manufacturers was the inherent unstable characteristics of the material. Early on, the Germans found out that their dyes would change color within a few years and tried unsuccessfully to solve the problem. That's why today we see yellow instead of a pearl white and a dull dark green instead of bright blue on our radios.
As a note of interest, the Bakelite Corporation claimed to have discovered the same dye and casting process as the Germans (catalin), but due to its fragile nature and its instability problems, they deemed the resulting material not suitable for production. Today, we can see other problems that catalin and its dyes have by examining our radios. As with urea, by not letting the compound set, the material is somewhat unstable and is subject to frequent stress lines. Additionally, again in part, because of the non-setting issue, catalin has the unfortunate characteristic of shrinking. Most catalin radios have shrunk up to one-half inch in the last sixty years. This is why glass dials in catalin radios are often cracked and stress lines emanate from their various holes. Also, the cabinet commonly has shrunk around the rigid metal chassis, causing more stress lines in the plastic, as well as sometimes rendering the chassis nearly impossible to remove without damaging the cabinet.
If catalin can be thought of as a direct descendent of bakelite, then beetle is a direct descendent of urea. Beetle was developed for the tableware industry during the late 1920s and was manufactured using various compounds as fillers and dyes. With catalin gaining in popularity, chemists began experimenting with urea-based compounds and using some of the processes developed for catalin. Although Beetle is a molded plastic and its compounds set, the resulting product was somewhat similar in appearance to catalin but much more stable. As with catalin, beetle could be created in many colors, mostly pastels and even swirled to give it a marbling effect.
Beetle first appeared in the radio industry around 1933 with the Kadette brand. As with urea and plaskon, we see the same problems arise in beetle radios. The lower temperatures used to set the compound did not completely vulcanize beetle and therefore it is prone to frequent stress lines. Another problem we find today is that constant low heat (from tubes, sunshine, lamps) over a period of time will cause separation in some of the swirls. This separation is often found on an open surface -- a side or top, but unlike stress lines, doesn't run to an edge.
In the years of the plastic boom before 1940, many new compounds were created and several were introduced into the radio industry. Notably, a celluloid derivative called Tenite was tried, but it tended to melt or warp under only moderate heat and didn't last long even when created as knobs or escutcheons. Polystyrene, nylon and others were around experimentally before the war but didn't make a pre-war showing in the radio world. Even before the interruption of World War II, the plastic industry was about to be hit with an entirely new process, and new era for manufacturing: a process called injection molding. Because of many factors, cost being number one, injection molding quickly became the process of choice for the industry. Although all of the "pre-war" plastics would survive the war, their fate was sealed. They were simply too expensive to make compared to injection molded plastics. So practically all were gone by 1950, and a golden era ended.
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